EP3500079B1 - Liquid cooling system for an electronic board comprising a cold plate and heat sinks linked to cold plate using flexible links - Google Patents

Description

The present invention relates to a liquid cooling system for an electronic card comprising at least one calculation processor.

Server compute blades generally have electronic boards that give off heat and therefore need to be cooled. Initially, these electronic boards were cooled by air. However, in the case of rack mountable servers, the air circulation is not sufficient to cool the electronic boards.

To solve this problem, fluidic cooling systems have been developed.

Among the known solutions for cooling electronic cards, the IBM company has developed a mixed cooling system 1 'of electronic cards 2 dual processors for a supercomputer, which is shown in the figure. figure 1 . Such a system comprises copper pipes 11 ′ containing a heat transfer liquid forming a liquid loop. However, the rigidity of the copper pipes 11 'does not allow the rapid disassembly of a single processor. In addition, the liquid loop ensures cooling of the processors only. The rest of the dissipated power is cooled by convection in the air, which is not optimal for the energy efficiency (PUE, acronym for “ Power Usage Effectiveness ”) of the supercomputer.

Other electronic card manufacturers offer liquid cooling systems dedicated only to processors. These integrate a heat sink, an integrated pump and an exchanger to extract the calories. Of course, such devices are not compatible with larger scale systems such as supercomputers for reasons of space.

The applicant has also developed a mixed 1 "cooling system (illustrated on figure 3 ) in which the electronic boards 2 are cooled by means of a cold aluminum plate 11 in which a coolant circulates, the cold plate 11 being interfaced with all the low and medium electronic components to be cooled, that is to say say all the components of an electronic card 3 excluding the high electronic components (typically processors and memory modules). Processors 23 (not visible on the figure 3 ) are the most restrictive components to cool (because they must remain accessible) and also the most dissipative. They cannot be interfaced with the cold plate 11 directly. In order to ensure thermal contact with the processors 23, each of them is interfaced with an intermediate heat sink 16 with heat pipes 160 (illustrated on figure 2 ). This is a phase change two-phase heat sink 16 (generally referred to in English by the terms " Heat Spreader CPU "), which conducts the heat from the processors 23 to the cold plate 11. The part of the heat pipes 160 in contact with the copper slab which interfaces the processor 23 constitutes the evaporator 162, while that in contact with the interface with the cold plate 11 constitutes the condenser 163. This solution is described in more detail in the patent applications. European EP 2770809 and EP 2770810 belonging to the Applicant.

• des limites thermiques spécifiques aux caloducs : l'écoulement à l'intérieur d'un caloduc est diphasique et est régi par cinq limites en termes d'écoulement, de viscosité, d'ébullition, d'entrainement, de capillarité) qui dépendent des dimensions des caloducs et de la puissance à évacuer.
• des limites mécaniques : l'augmentation du nombre de caloducs entraine une augmentation de la rigidité de l'ensemble. Or, afin de compenser les écarts de tolérances il est indispensable que le dissipateur se déforme suffisamment.
• un nombre élevé d'interfaces thermiques amovibles : des contacts thermiques doivent être assurés entre la plaque froide et le dissipateur thermique d'une part, et entre le dissipateur thermique et le processeur. Ces contacts thermiques sont dans la solution actuelle mise en place par le demandeur garantis par l'utilisation de graisse conductrice, présentant l'inconvénient de générer un gradient de température élevé.
• la complexité et le coût de la solution globale : les surfaces d'échanges solide/fluide sont actuellement au niveau de la plaque froide. La complexité de celle-ci au niveau des dissipateurs thermiques augmente considérablement les usinages dans la plaque froide et ainsi le coût de fabrication.

This solution for cooling processors using heat pipes also has drawbacks, and in particular:

• thermal limits specific to heat pipes: the flow inside a heat pipe is two-phase and is governed by five limits in terms of flow, viscosity, boiling, entrainment, capillarity) which depend on the dimensions of the heat pipes and the power to be removed.
• mechanical limits: the increase in the number of heat pipes leads to an increase in the rigidity of the assembly. However, in order to compensate for the deviations in tolerances, it is essential that the dissipator deforms sufficiently.
• a high number of removable thermal interfaces: thermal contacts must be ensured between the cold plate and the heat sink on the one hand, and between the heat sink and the processor. These thermal contacts are in the current solution implemented by the applicant guaranteed by the use of conductive grease, having the drawback of generating a high temperature gradient.
• the complexity and the cost of the global solution: the solid / fluid exchange surfaces are currently at the level of the cold plate. The complexity of this at the level of the heat sinks considerably increases the machining operations in the cold plate and thus the manufacturing cost.

To resolve the aforementioned defects and drawbacks, the applicant has therefore developed a cooling system for an electronic card which is entirely liquid, comprising a cold plate supplied with heat transfer fluid via a water path internal to the cold plate, and a cold plate. plurality of heat sinks connected in flexible connections with the water path internal to the cold plate. These flexible connections form a flexible network coupled to the network of rigid channels of the cold plate supplied with heat transfer fluid (typically glycol water), thus allowing the supply of heat transfer fluid to the heat sinks. This network must be coupled to the cold plate system allowing the cooling of the rest of the electronic board.

To optimize the cooling of the processor as much as possible, the coolant must be brought as close as possible to the heat source. To this end, the Applicant has specifically developed a single-phase heat sink comprising a cooling unit made of thermally conductive material which can be supplied with heat transfer fluid. The heat source formed by the processor will therefore be directly interfaced with this cooling unit ( also designated in the examples by the term “water block ”) supplied with heat transfer fluid taken from the cold plate. Such an integrated cooling system meets the constraints of thermal efficiency, mechanical compactness and maintainability necessary for this type of high performance computer hardware.

• une plaque froide présentant des dimensions extérieures sensiblement égales à celles dudit support de la carte électronique de sorte qu'elle recouvre l'intégralité du support et lesdits composants électroniques bas et moyens, ladite plaque froide étant une plaque réalisée en un matériau thermique conducteur et comprenant un circuit primaire de refroidissement avec des canaux principaux (de préférence rigides) à l'intérieur desquels circule un fluide caloporteur, l'alimentation en fluide caloporteur dans ladite plaque froide étant réalisée via un connecteur d'entrée et la sortie dudit fluide caloporteur hors de la plaque froide se faisant via un connecteur de sortie,
• une pluralité de dissipateurs thermiques comprenant chacun une zone d'échange thermique principale apte à venir en appui contre un composant électronique haut,

ledit système de refroidissement liquide étant caractérisé en ce qu'il comporte en outre un circuit secondaire de canaux secondaires flexibles connectés aux canaux principaux du circuit primaire par des connecteurs coudés fixés dans ladite plaque froide (par exemple par vissage dans la plaque froide), et
en ce que lesdits dissipateurs thermiques (12) sont des dissipateurs thermiques monophasiques qui comprennent chacun :

• ▪ un bloc de refroidissement en matériau thermoconducteur (typiquement en aluminium ou alliage d'aluminium) comprenant une partie inférieure constituant la zone d'échange thermique principale, une partie intermédiaire dite de répartition et une partie supérieure connectée à la plaque froide,
• ▪ un canal d'entrée et un canal de sortie qui sont connectés d'une part à la partie supérieure dudit bloc de refroidissement par l'intermédiaire respectivement d'un connecteur d'entrée et d'un connecteur de sortie, et d'autre part à un canal secondaire flexible du circuit secondaire via un connecteur coudé, de sorte que ledit bloc de refroidissement est alimenté par ledit fluide caloporteur circulant dans ladite plaque froide, lesdits connecteurs coudés étant aptes à permettre la rotation desdits canaux d'entrée et de sortie par rapport audit canal secondaire flexible auquel ils sont connectés, et

en ce que ledit bloc de refroidissement comprend en outre:

• ▪ une fente traversante située dans la partie intermédiaire pour répartir de manière homogène l'écoulement dudit fluide caloporteur en provenance de la partie supérieure sous forme de jet centré vers
• ▪ une plaque support située dans la zone d'échange thermique principale et comportant une partie centrale creuse avec une zone munie d'ailettes ou de picots pour générer de la turbulence dans le régime d'écoulement dudit fluide caloporteur et une zone périphérique à ladite zone munie d'ailettes ou de picots pour recueillir le fluide caloporteur et le diriger vers ledit connecteur de sortie.

More particularly, the subject of the present invention is therefore a liquid cooling system for an electronic card comprising a support, a plurality of electronic components fixed on said support breaking down into low and medium electronic components and high electronic components (preferably high electronic components). processors), said system comprising:

• a cold plate having external dimensions substantially equal to those of said support of the electronic card so that it covers the entire support and said low and middle electronic components, said cold plate being a plate made of a thermally conductive material and comprising a primary cooling circuit with main channels (preferably rigid) inside which circulates a heat transfer fluid, the supply of heat transfer fluid into said cold plate being carried out via an inlet connector and the outlet of said fluid coolant outside the cold plate via an output connector,
• a plurality of heat sinks each comprising a main heat exchange zone able to bear against a high electronic component,

said liquid cooling system being characterized in that it further comprises a secondary circuit of flexible secondary channels connected to the main channels of the primary circuit by elbow connectors fixed in said cold plate (for example by screwing into the cold plate), and
in that said heat sinks (12) are single phase heat sinks which each comprise:

• ▪ a cooling block made of thermally conductive material (typically aluminum or aluminum alloy) comprising a lower part constituting the main heat exchange zone, an intermediate so-called distribution part and an upper part connected to the cold plate,
• ▪ an input channel and an output channel which are connected on the one hand to the upper part of said cooling unit via an input connector and an output connector respectively, and on the other hand part to a flexible secondary channel of the secondary circuit via an elbow connector, so that said cooling unit is supplied by said heat transfer fluid circulating in said cold plate, said elbow connectors being able to allow rotation of said inlet and outlet channels with respect to said flexible secondary channel to which they are connected, and

in that said cooling block further comprises:

• ▪ a through slot located in the intermediate part to distribute evenly the flow of said heat transfer fluid from the upper part in the form of a jet centered towards
• ▪ a support plate located in the main heat exchange zone and comprising a hollow central part with a zone provided with fins or pins to generate turbulence in the flow regime of said heat transfer fluid and a zone peripheral to said zone provided with fins or pins to collect the heat transfer fluid and direct it towards said outlet connector.

The cooling system according to the invention thus makes it possible to guarantee the cooling of all the components of the electronic card, and this by liquid means whatever the nature of the electronic components: the low and medium components by the cold plate and the so-called components. highs such as processors and memory modules by single phase cooling block heat sinks.

By low and medium electronic components is meant, within the meaning of the present invention, any component of the electronic card having a height less than a threshold height, below which it can be cooled by the cooling circuit of the cold plate. As regards the low and medium electronic components, it is generally a power supply or a voltage regulator.

By high electronic components is meant, within the meaning of the present invention, any component of the electronic card which is not cooled by the cooling circuit of the cold plate because they must remain accessible without dismantling the cold plate. These are electronic components requiring rapid maintenance such as processors or memory modules.

The cooling system according to the invention, due to its structure with cooling units connected in flexible connections with the cooling circuit of the cold plate, allows great flexibility for the disassembly of processors and guarantees reliable connections after a large number of disassembly operation cycles. A seal at 10 bars is guaranteed by the cooling system according to the invention, including after several dismantling operations.

The cooling system according to the invention, due to its structure with cooling units connected in flexible links with the cooling circuit of the cold plate, allows the installation of a plurality of heat sinks in series or in parallel, for example six in number.

The heat sink of the cooling system according to the invention must moreover itself comply with a size constraint defined by the size of the processors and by the space available on the cold plates to judiciously distribute the cooling fluid.

The heat sink of the cooling system according to the invention also makes it possible to meet the constraints of mass production, because of its simplicity of manufacture and of assembly by flexible connections with the cold plate.

The middle part of the cooling block has a slot. In this configuration, the heat transfer fluid, when it arrives in the cooling unit, passes through a very fine thin slit or blade, which allows its equitable distribution in the exchange surface through the fins. The shape of this distributor and its distance from the fins are studied so as to obtain the largest possible Reynolds number in the space available.

Preferably, it will be chosen to orient the slot of the intermediate part of the cooling unit perpendicular to the direction of the fins, so as to maximize the coefficient of exchange between the fluid and the solid surface of the fins.

According to an advantageous embodiment of the cooling block, the intermediate part of the cooling block cooling may consist of a distribution plate in which the through slot is made.

In such an embodiment, the distribution plate may be in the substantially form of a rectangular parallelepiped, one of the sides of which is provided with a step which fits into the part of the peripheral zone of the zone of. main heat exchange is located under the input connector without covering the part of the peripheral area under said output connector.

According to an advantageous embodiment of the cooling unit, fins, and preferably straight fins, will be used for the support plate of the cooling unit. In this case, the straight fins may have a thickness of 0.2 mm and be spaced from each other by a distance of 0.4 mm. The distance between 2 fins is preferably also 0.2 mm.

The use of fins makes it possible on the one hand to increase the exchange surface, and on the other hand to increase the turbulence of the flow in order to improve the heat exchange coefficient.

The straight fins make it possible to create a flow by jet (known under the name in English " liquid-jet ") and to obtain turbulent flow regimes even with very low velocities and pressure losses.

The liquid cooling system according to the invention therefore makes it possible to combine a high heat exchange surface and an optimized convective coefficient at the center of the processor by virtue of its flow by a centered jet. It also makes it possible to obtain a reduction in the hydraulic diameter and the passage sections, which offers greater speed to the fluid and thus the convective exchanges are improved. This type of flow also makes it possible to center the peak of the convective heat transfer, unlike longitudinal flows, which do not optimize the exchange as close as possible to the processor.

• la figure 1 montre un système de refroidissement mixte d'une carte électronique double processeur de l'art antérieur;
• la figure 2 un dissipateur thermique diphasique d'un système de refroidissement de carte électronique connu de l'art antérieur et appartenant au Demandeur,
• la figure 3 montre le système de refroidissement connu de l'art antérieur intégrant le dissipateur thermique illustré sur la figure 2,
• la figure 4 est une représentation schématique du système de refroidissement liquide selon l'invention, montrant la répartition du fluide caloporteur dans les canaux secondaires flexibles au travers des dissipateurs thermiques ;
• la figure 5 est une photographie montrant, dans un système de refroidissement liquide selon l'invention comportant une pluralité de ces blocs de refroidissement, la cinématique de rotation de l'un de ces blocs par rapport à un canal du circuit secondaire de refroidissement
• la figure 6 est une vue éclatée schématique d'un mode de réalisation d'un dissipateur thermique utilisable dans un système de refroidissement liquide selon l'invention ;
• la figure 7 est une photographie montrant le montage complet du système de refroidissement liquide selon l'invention sur trois cartes électroniques comportant chacune un processeur ;
• La figure 8 montre le résultat d'une simulation numérique de l'évolution de la perte de charge dans le circuit de refroidissement primaire de la plaque froide, faisant partie d'un système de refroidissement liquide selon l'invention à 3 blocs de refroidissement ;
• la figure 9 est une représentation schématique du modèle hydraulique simplifié du système de refroidissement liquide selon l'invention correspondant à celui pour lequel la simulation numérique illustrée sur la figure 9 a été réalisée ;
• La figure 10 montre le résultat d'une simulation numérique de l'évolution du champ de vitesses dans le circuit de refroidissement primaire de la plaque froide, faisant partie d'un système de refroidissement liquide selon l'invention correspondant à celui des figures 9 et 10 ;
• La figure 11 montre le résultat d'une simulation numérique de l'échauffement du fluide caloporteur dans le circuit de refroidissement primaire de la plaque froide, faisant partie d'un système de refroidissement liquide selon l'invention correspondant à celui des figures 9, 10 et 11 ; dans cette figure on observe également l'échauffement du fluide dans les tuyaux représentatif du bloc de refroidissement ;
• La figure 12 montre le résultat du champ de températures de la plaque froide (vue de dessous, c'est-à-dire du côté de la carte électronique).

Other advantages and features of the present invention will result from the examples below which will follow, given by way of non-limiting example and with reference to the appended figures:

• the figure 1 shows a mixed cooling system of a dual processor electronic card of the prior art;
• the figure 2 a two-phase heat sink of an electronic card cooling system known from the prior art and belonging to the Applicant,
• the figure 3 shows the cooling system known from the prior art incorporating the heat sink illustrated on figure 2 ,
• the figure 4 is a schematic representation of the liquid cooling system according to the invention, showing the distribution of the heat transfer fluid in the flexible secondary channels through the heat sinks;
• the figure 5 is a photograph showing, in a liquid cooling system according to the invention comprising a plurality of these cooling blocks, the kinematics of rotation of one of these blocks with respect to a channel of the secondary cooling circuit
• the figure 6 is a schematic exploded view of an embodiment of a heat sink usable in a liquid cooling system according to the invention;
• the figure 7 is a photograph showing the complete assembly of the liquid cooling system according to the invention on three electronic boards each comprising a processor;
• The figure 8 shows the result of a numerical simulation of the evolution of the pressure drop in the circuit of primary cooling of the cold plate, forming part of a liquid cooling system according to the invention with 3 cooling blocks;
• the figure 9 is a schematic representation of the simplified hydraulic model of the liquid cooling system according to the invention corresponding to that for which the digital simulation illustrated on figure 9 was realized ;
• The figure 10 shows the result of a numerical simulation of the evolution of the speed field in the primary cooling circuit of the cold plate, forming part of a liquid cooling system according to the invention corresponding to that of the figures 9 and 10;
• The figure 11 shows the result of a digital simulation of the heating of the heat transfer fluid in the primary cooling circuit of the cold plate, forming part of a liquid cooling system according to the invention corresponding to that of the figures 9 , 10 and 11 ; in this figure, the heating of the fluid in the pipes representative of the cooling unit is also observed;
• The figure 12 shows the result of the temperature field of the cold plate (seen from below, that is to say from the side of the electronic board).

For greater clarity, identical or similar elements are identified in these figures by identical reference signs in all of the figures.

The figures 1 to 3 are described in more detail in the part of the preceding description relating to the description of the solutions known from the prior art.

The figures 4 to 8 are described in more detail in the part of the description which follows, relating to the description detail of an embodiment of the liquid cooling system according to the invention.

The figures 9 to 14 are described in more detail in the examples which follow, which illustrate the invention without limiting its scope.

DESCRIPTION OF AN EMBODIMENT

The figure 4 schematically shows an embodiment of a liquid cooling system 1 according to the invention comprising three heat sinks 12. The figure 4 shows more particularly the distribution of the heat transfer fluid 112 in a secondary network of flexible secondary channels 1111 through the heat sinks 12.

The complete assembly of the liquid cooling system 1 according to the invention on an electronic card 2 comprising three processors 23 (visible on the figure 5 ) is shown in the photograph of the figure 8 . The electronic card 2 comprises, in addition to the processors 23, a plurality of low and medium electronic components 22 (visible by transparency on the figure 5 ) fixed on a support 21.

The figure 8 shows that the liquid cooling system according to the invention comprises on the one hand a cold plate 11 having external dimensions substantially equal to those of said support of the electronic card 2 so that it covers the entirety of the support 21 and of the components low electronics and means 22 which are attached thereto, and on the other hand three heat sinks 12 each comprising a main heat exchange zone 121 (visible on the figure 6 ) able to come to rest against a processor 23.

The cold plate 11 can advantageously be a plate made of a thermally conductive material such as aluminum. It includes a primary cooling circuit 110 (visible on the simulation of the figure 8 ) with main channels 1101 inside which circulates a heat transfer fluid 112 such as glycol water. The supply of heat transfer fluid 112 into the cold plate 11 is carried out via an inlet connector 113 and the outlet of the heat transfer fluid 112 from the cold plate 11 is made via an outlet connector 114.

The figure 5 also shows how the liquid cooling system 1 according to the invention is associated with the primary cooling circuit 110 of the cold plate, thanks to single-phase heat sinks 12 (also visible on the figure 4 ) and a secondary circuit 111 of flexible secondary channels 1111 connected to the main channels 1101 of the primary circuit 110 by elbow connectors 1112 screwed into the cold plate 11.

• ▪ un bloc de refroidissement 120 en matériau thermoconducteur
• ▪ un canal d'entrée 3 et un canal de sortie 4 qui sont connectés d'une part à la partie supérieure 123 dudit bloc de refroidissement 120 par l'intermédiaire respectivement d'un connecteur d'entrée 5 et d'un connecteur de sortie 6, et d'autre part à un canal secondaire flexible 1111 du circuit secondaire 111 via un connecteur coudé 1223, 1224.

The heat sinks 12 are single phase heat sinks which each include (see also figure 4 ):

• ▪ a cooling block 120 in thermally conductive material
• ▪ an input channel 3 and an output channel 4 which are connected on the one hand to the upper part 123 of said cooling unit 120 by means of an input connector 5 and an output connector respectively 6, and on the other hand to a flexible secondary channel 1111 of the secondary circuit 111 via an elbow connector 1223, 1224.

The structure of the heat sink of the cooling system according to the invention is therefore such that the cooling unit is supplied by the heat transfer fluid 112 circulating in said cold plate 11.

The figure 5 clearly shows that these angled connectors 1223, 1224 allow the rotation of the inlet and outlet channels 3, 4 with respect to the flexible secondary channel 1111 to which they are connected.

The figure 6 is a schematic exploded view of an embodiment of a heat sink 12 usable in a liquid cooling system 1 according to the invention. This figure shows that the heat sink that can be used in the context of the invention comprises a cooling unit 120 made of thermally conductive material comprising a lower part constituting a main heat exchange zone 121, an intermediate part 122 called the distribution part and an upper part 123 connected to the cold plate 11. A through slot 8 is located in the intermediate part 122 to evenly distribute the flow of the heat transfer fluid 112 from the upper part 123 in the form of a jet centered towards a support plate 9 located in the main heat exchange zone 121. This support plate 9 and comprising a hollow central part with a zone provided with fins 910 (the fins are not visible on the fig.6 ) to generate turbulence in the flow regime of said coolant 112 and a peripheral zone 911 to the zone provided with fins 910 to collect the coolant 112 and direct it towards said outlet connector 6.

According to an advantageous embodiment of the cooling unit, fins 910 will be used for the support plate of the cooling unit, and preferably: straight fins. In this case, the straight fins may have a thickness of 0.2 mm and be spaced from each other by a distance of 0.4 mm.

According to an advantageous embodiment of the cooling unit, the through slot 8 is perpendicular to the direction of the fins 910.

According to an advantageous embodiment of the cooling unit, the intermediate part 122 consists of a distribution plate 7 in which the through slot 8 is formed. The distribution plate 7 is in the substantially form of a rectangular parallelepiped with one of the sides is provided with a step 71 fitting into the part of the peripheral zone 911 of the main heat exchange zone 121 located under the input connector 5, without covering the part of the peripheral zone 911 located under the output connector 6.

Thanks to the liquid cooling system according to the invention 1, the processors will be 10 ° C less hot than if the known cooling system of the prior art shown in FIG. figure 3 (heat pipe system: see also figure 2 ) with heat pipes. Thanks to the liquid cooling system according to the invention, it is therefore possible to cool more powerful processors.

EXAMPLES

The hydraulic behavior of the liquid cooling system according to the invention (with three processors) as shown in the diagrams is simulated. figures 4 to 8 .

CALCULATION CONDITIONS

• Modèle simulant la conduction et la convection avec le fluide caloporteur, la convection naturelle et le rayonnement avec l'air ambiant autour de la plaque froide étant négligés ;
• Débit entrée de lame = 3 l/min (5.10^-5 m³/s);
• Température du fluide caloporteur en entrée de lame = 44°C ;
• Fluide caloporteur utilisé : PEG MB633 (mélange eau + PEG)

Cibles de perte de charges pour équilibrage des lames : 70kPa Cible de ΔT_{entrée-sortie} sur la lame : environ 7°CThe calculation conditions are as follows:

• Model simulating conduction and convection with the heat transfer fluid, natural convection and radiation with ambient air around the cold plate being neglected;
• Blade inlet flow rate = 3 l / min (5.10 ^-5 m ³ / s);
• Temperature of the heat transfer fluid at the blade inlet = 44 ° C;
• Heat transfer fluid used: PEG MB633 (water + PEG mixture)

Pressure drop targets for blade balancing: 70kPa _Input-output ΔT target on the blade: approximately 7 ° C

EXAMPLE 1 : hydraulic simulation of the cooling system according to the invention with 3 cooling blocks (as shown in FIGS. 4 to 7).

The result of the numerical simulation of the evolution of the pressure drop in the primary cooling circuit of the cold plate is shown on the figure 8 . Optimization work made it possible to reach the target of around 70 kPa of pressure drop in the cold plate at 3l / min (as shown in figure 8 and scale).

The pressure drop target for blade balancing is 70kPa. The calculated value of the overall pressure drop of the cold plate is of the order of 75Kpa, which is close to the target value.

EXAMPLE 2 : thermal simulation of the cooling system according to the invention with 3 cooling blocks (as represented in FIGS. 4 to 7).

The figure 11 shows the result of a numerical simulation of the heating of the heat transfer fluid in the primary cooling circuit of the cold plate, and the figure 12 shows the result of the temperature field of the cold plate (view from below). Heat sources are applied directly to the cold plate at the location of the middle and bottom components. The result of the simulation gives a plate temperature at the interface with each of the components (medium and low).

One observes a heating of the fluid inside the cold plate, the entry of the cold plate is well at 44 ° C since it is an input data of calculation (limiting condition). The output is around 52 ° C. There is therefore a temperature gradient between the inlet and the outlet of the fluid of approximately 8 ° C.

Claims (7)

1. A liquid cooling system (1) for an electronic board (2) comprising a substrate (21), a plurality of electronic components (22, 23) secured to said substrate (21) broken down into low-level and mid-level electronic components (22) and into high-level electronic components (23), said system (1) comprising:

   • a cold plate (11) having external dimensions substantially equal to those of said substrate (21) of the electronic board (2) such that it covers the entire substrate (21) and said low-level and mid-level electronic components (22), said cold plate (11) being a plate made from a heat conducting material and comprising a primary cooling circuit (110) with main channels (1101) inside which a heat transfer fluid (112) flows, the supply of heat transfer fluid (112) in said cold plate (11) being done via an inlet connector (113) and the exit of said heat transfer fluid (112) from the cold plate (11) being done via an outlet connector (114),

   • a plurality of heat sinks (12) each comprising a main heat exchange zone (121) able to bear against a high-level electronic component (23),

   said liquid cooling system (1) being characterized in that it further includes a secondary circuit (111) of flexible secondary channels (1111) connected to the main channels (1101) of the primary circuit (111) by angled connectors (1112) secured in said cold plate (11), and
   in that said heat sinks (12) are single-phase heat sinks which each comprise:

   ▪ a cooling block (120) made from a heat conducting material comprising a lower part making up the main heat exchange zone (121), an intermediate part (122) called the distribution part and an upper part (123) connected to the cold plate (11),

   ▪ an inlet channel (3) and an outlet channel (4) which are connected on the one hand to the upper part (123) of said cooling block (120) respectively by means of an inlet connector (5) and of an outlet connector (6), and on the other hand to a flexible secondary channel (1111) of the secondary circuit (111) via an angled connector (1223, 1224), such that said cooling block (120) is supplied by said heat transfer fluid (112) flowing in said cold plate (11), said angled connectors (1223, 1224) being able to allow the rotation of said inlet and outlet channels (3, 4) relative to said flexible secondary channel (1111) to which they are connected, and

   in that the cooling block (120) further comprises:

   ▪ a through slot (8) located in the intermediate part (122) to uniformly distribute the flow of said heat transfer fluid (112) coming from the upper part (123) in the form of a centered jet toward

   ▪ a support plate (9) located in the main heat exchange zone (121) and including a hollow central part with a zone provided with fins (910) in order to generate turbulence in the flow state of said heat transfer fluid (112) and a zone (911) peripheral to said zone provided with fins (910) to collect the heat transfer fluid (112) and orient it toward said outlet connector (6).
2. The liquid cooling system (1) according to claim 1, wherein the fins (910) are straight fins.
3. The liquid cooling system (1) according to claim 2, wherein the fins (910) have a thickness of 0.2 mm and are spaced apart from one another by a distance of 0.4 mm.
4. The liquid cooling system (1) according to any one of claims 1 to 3, wherein the orientation of said slot (8) is perpendicular to the direction of the fins (910).
5. The liquid cooling system (1) according to any one of claims 1 to 4, wherein the intermediate part (122) is made up of a distribution plate (7) in which the through slot (8) is formed.
6. The liquid cooling system (1) according to claim 5, wherein said distribution plate (7) is in the approximate form of a rectangular parallelepiped, one of the sides of which is provided with a step (71) that fits into the part of the peripheral zone (911) of the main heat exchange zone (121) located below said inlet connector (5), without covering the part of the peripheral zone (911) located below said outlet connector (6).
7. The liquid cooling system (1) according to any one of the preceding claims, wherein high-level electronic components (23) are processors.

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